Characteristics of CO2 foam plugging and migration: Implications for geological carbon storage and utilization in fractured reservoirs

Abstract

Fractured reservoirs exhibit heterogeneity and high conductivity, posing challenges to the application of low-carbon and clean production technologies. In this study, the flow and plugging characteristics of CO2 foam in fractured cores were analyzed in physical fracture cores and visual slab fracture models. The influence of surface roughness and fracture openings on foam flow and plugging efficiency were studied. Results show that polymer-enhanced foam displays a higher-pressure drop in a single core with a small fracture opening. With increasing fracture opening, the plugging capacity of the polymer-enhanced foam gradually decreases to that of ordinary foam. In parallel fractures of different openings, ordinary foam is better able to regulate the flow, whereas the conformance control of polymer-enhanced is more robust. Prolonged foam flow in the fractures leads to foam collapse, especially for small fracture openings and high roughness. For such a core, the difference in distance lapsed by the upper and lower ends of the polymer-enhanced foam front is greater than that of the ordinary foam, and the bubble collapse during migration is less. For a given surface roughness, the smaller the fracture opening, the greater the resistance to foam flow. However, the resistance brought forth by surface roughness is greater, for a given fracture opening. Foam flow in the fracture is analyzed in terms of the forces acting on the foam. Understanding foam flow resistance is a key to preventing gas channeling, expanding sweep range and improving the oil washing efficiency.